Stanley and Nolan lure readers with this playful puzzle. Rusty, an art student who comes to the city art museum to copy the works of Dutch masters, realizes that a kitchen maid in one painting and a gentleman in another have fallen in love. Of course the affair is hopeless: ``there they were, trapped in their different worlds, frozen in time.'' Nosy neighboring portraits comment snidely (``the stern gentleman in black believed the servant girl to be at fault for looking over her shoulder in such a pleasant way''), but worse is to come: the museum directors move The Kitchen Maid to another room. But through her own art Rusty transcends all barriers: she unites the lovers in a single painting. Hats off to Nolan for his thorough research and credible renderings of paintings in the style of artists ranging from Rembrandt to Picasso (a note lists all 19 painters represented, and further states that the frames are modeled on those in the Yale Center for British Art). Stanley's supple storytelling admits a fresh, romantic grasp of the possibilities of art and imagination. Ages 5-8. (Mar.)